In recent years, as a consequence of an increase in the demand for fish meat as the source of proteins, a need has been felt for establishment of a method which permits fish meat stock to be preserved in the state having the functional characteristics of fresh fish meat retained intact for a long period of time.
For the purpose of such preservation, a method has previously been used which comprises the steps of slicing meat from the fish body, washing the meat slices with water, grinding the washed meat slices with a polyphosphate and a saccharide or sugar alcohol and freezing the resultant ground meat mixture to produce frozen SURIMI. This method is effective in preventing the fish meat from losing the functional characteristics of fresh fish meat during the frozen storage and in preventing the fish meat from degradation by freezing. Nevertheless this method requires that the fish meat be stored in a frozen state and, therefore, entails the disadvantage that the expense for freezing the fish meat and the expense for frozen storage of fish meat in the phase of distribution in the market are great.
As a result, with a view toward ensuring simple handling during market of distribution, there has recently been proposed a method for producing a fish meat powder retaining the functional characteristics of the fresh fish meat used as the raw material by preparing fresh fish meat or frozen SURIMI in the form of a sol and subsequently spray drying the fish meat sol. According to this method, however, the fish meat being prepared in the form of sol must be diluted with added water to a solids content (about 10 percent) so as to facilitate spray drying. The addition of extra water brings about the disadvantage of an additional energy requirement for the dehydration of fish meat by spray drying.
For the drying of foodstuffs, there are generally employed means such as spray drying, freez-drying and vacuum drying, depending on the attributes and forms of the particular foodstuffs. In the case of fish meat, because of the peculiar properties of fish meat such as, for example, high susceptibility of fish meat proteins to denaturation and the high molecular weights of the fish meat proteins compared with those of other foodstuffs, it is considered extremely difficult from the practical point of view to have the fish meat dried in such a way that the functional characteristics of fresh fish meat will be retained intact throughout the drying treatment. When a fish meat powder retaining the aforementioned characteristics is to be produced by use of the freeze-drying process which entails less denaturation of fish meat proteins, for example, the frozen fish meat raw material is subjected to heat drying under vacuum. Thus, this process has the disadvantage of energy requirements in the two separate steps of freezing and drying. Furthermore, since this process is carried out batch-wise, the production efficiency thereof is too low to render the possible practicable.
Although U.S. Pat. No. 3,093,488 (Graham et al.) discloses a process of preparing a porous dehydrated fish meat product by gasifying a fish meat sol, forming it into a stable foam and dehydrating the foam, it has been found as shown in the "Comparative Example" described hereinafter that a fish meat powder cannot be produced by the Graham process which retains the functional characteristics of fresh fish meat.